This application is a request to continue and extend our investigations of the aging nervous system. Both cross-sectional and longitudinal approaches will be used to obtain a variety of electrophysiological and behavioral measures from 60 health subjects ranging in age from 20-70 years to assess changes in the CNS which occur with advancing age. Studies are included which are designed to measure electrophysiological correlates of age related changes in inhibitory deficits, speed and efficiency of central processing, learning, attention, and habituation. While averaged visually evoked responses (VERs) will be primarily studied, extensive analyses will be made of the single trial responses from which the VERs are constructed. Analysis of single trial responses will provide a measure of brain response variability across age and will determine whether changes in VER amplitude associated with psychological conditions such as attention and habituation are related to variability or amplitude of the single trial responses. The results of these studies will also provide normal control data which can be used by ourselves and others for diagnostic procedures with clinical patients.